A so-called flange joint is employed for connecting pipes by coupling flange parts provided at end portions of the pipes, and as shown in Patent Literature 1, a type of flange joint is known that includes a coupling ring externally fitted to a facing flange part for pushing an inclined surface provided at each flange part toward a radial direction, compressing to couple the flange parts with a component force in an axial direction caused at the occasion, and arranging the pipes in series. A feature of the flange joint using the coupling ring is to be able to shorten a length in the axial direction as much as possible.